Electrical transmission system



Dec. 2 7,l 1927, 1,654,084

M. KIFN ELECTRICAL TRANSMISSION SYSTEM Filed June 2. 1926 y Affi/- Patented ldecM lt', i937 unrrnio sTATnS PATENT OFFICE.

MA BEEN, F SIEMENBSTADT, NEAR BERliIlSf, GERMANY, .ASSIGNOR TO SIEMENS &

H ALBIE AKIIENGEEEELLSCHAFT, OF GERMAN COMPANY.

SIEEVIENSSTADT, hTEAR BERLIN,

GERMANY, A.

ELECTRICAL TRANSMISSION" SYSTEM.

Application ilec'l .Tune 22, 1926, VSerial No. 117,658, and in Germany July 31, 1925.

rlhis invention relates to electrical trans inission systems, particularly systems einploying quaddcd cable.

As is Well lnioivn in the telephone art, it is often customary to combine two metallic circuits, called side circuits, to give a third circuit, known as the phantom circuit7 so that three independent sima-king` circuits are termed b v the use et tivo pairs of Wires. hln such systems it oiten desirable to ein` ploy cables tor the. transmission line9 tha tivo pairs oit ivi res which malte up each `-@group et tivo side circuits and a phantom circuit beingknown as a quad.

In the cables the ilour wires are stranded together ina particular nia-nner to give a detinite characteristi(:. The most 'tainiliar ot these strandintT systems are the Diese!- horsthiartin and lthe Star systems. Lines composed oi' conductors stranded ai'cordinggv to either et these syst-ems have the disadvantage that ou account oit the geometrical arrangenu-nit oi: the conductors, the ratio ot the working` capacity ot the phantom circuit to that oi the side circuit tilted.

ller inany purposes it is desirabIi-i to he able to control the ratio oit' phantom to side circuit capacities. For example, it is iinportant 'tliat the attenuation ot al! the cir cuits should he equal, so that the repeater spaeiiui` established in the side ci rcuitff-i can also he used Ator the phantoni circuits Without :in v modification. Similarly, ior economical reasons9 the cnt-oit 'frequency should` he made equal .tor both circuits. lil/ith 'telephone cables ot 'the type known heretofore the cut-ott' vfrequency has necessarily been higher tor the iiihantoin circuits than :tor the side circuits. This is due to the 'tact that the phantom capacity niust be a given inuitiple oi the side circuit capacity when using.;l a single type oit stranding. For example, the ratio of phantom circuit to side circuit capacity;7 igor the ordinary Dieselliorst--Martin stranding` is of the order oit 1.5 to 1.7, averaging about 1.6 and With the Star sym teni of the order ci 2.7 to 2.9 averaging about 2.5i. Moreover, since the ratio oit the ohinic resistanees ot the phantoin circuits and the side circuits are fixed and the loading; coil spacing for the phantom circuits and the side circuits is usually inade equal Afor econoinical reasons, there has, hitherto, been left only one alternative, that is, to compromise between the attenuation and the cutoil1 trequencies which were desired. rlhis led to uneconoinical conditions.

An object ot this invention is to control the ratio of the phantom circuit capacity to the side circuit capacity in a quadded cable system..

it further object of the invention is to nialie the phantom circuit transmission characteristic siinilar to that of the side circuit transniission characteristic by the use o'.t a simple, economi-cal and `practical method.

iliccording` to a i'eatureot this invention, lines are composed of sect-ions stranded in diil'ei'ent manners so that the ratio oitl the working capacities can he varied arlaitrarily within certain limits. In order that the line may be somewhat similar to a homogeneous line in its cllect the sections are preferably chosen to he small with respect to the Wave length oli the transmitted frequencies. .For example, in cables loaded accordingl to the lupin system, cai-.h loaded section should he composed ol" several dii'lfeifently stranded portions.

ln accordance with another 'feature of this invention the portions oi.:` the line stranded accordii'nr to the diiiferent systems are so proportioned with respect to one another as 'to give the saine transmission charaeteris tics iter both the phantom and side circuits.

In the preferred embodiment oit the invention part of the line is stranded accord ingr to the Star sjstcin und the remainder according` to the l)ieselhorst-h/Iartin system, the ratio of the portions being determined as eiqalained below to give the desired chan acteristics. It it is desired to use other methods ot stranding the saine inethod oit calculating;l the relative proportions may he used.

As stated above it is desirable that:

l. The attenuation et the phantom and side circuits be equal.

f. That the cut-oilI frequencies lf'or the phantom and side eircui ts he equal.

3. 'lhat the loading` coil spacing` be the saine. p

As a lirst approximation it may be as sinned that with loaded lines, the attenua` ice tion is independent of the leakance. 1With this assumption it followsthat in order to obtain the desired characteristics the following conditions are necessary:

These give the following ratio of characteristic impedanees,

I-n these equations Cp, Lp, Zn and Cr, LF, ZS represent the capacity, inductance and characteristic impedance of the phantom and side circuits respectively.

The'above ratio of inductances can always be obtained by controlling the loading and according to this invention. by connecting` together a certain length of Star stranded cable witha definite proportional length of` Dieselhorst-Martin stranded cable, the radio can be vmade to approximately equal th'e value two, and thus fuiill the conditions f both types of cables have the same side circuit capacities, the ratio of the overall lphantom to side'eircuit capacities is:

'Since this ratio is required to have the value 2 Therefore in accordance with this invention, one-third of the loading section should be composed of Star stranded cable and two-thirds of Dieselhorst-Martin stranded cable. y

These and other features and objects of the invention can be more readily understood by reference to the following detailed description in connection with the drawing in which: Figs. l and 2 illustrate the methods of quadding accordingr to the Diesel.- horst-Martin and Star systems resliectively and Fig. 3 shows a portion of a transmission line arranged in accordance with this invent-ion.

Fig. l shows a quad composed of two metallic circuits, n., a and Zi, l). In accordance with the DieselhorstMartin system these are stranded by first twisting together the two wires making up each pair and then twisting the two pairs together to make a rope of four wires. iVhen more than one quad is combined in a cable, two quads formed shown are twisted together and so on.

2 shows method of sti-ending according to the Star system in which a quad composed of two pairs n., (z, and l), b is stranded by simultaneously twisting the four wir .s together Y Fig. shows diagrannnatically two loading sections el and 5 of a transmission sys tem associated with loading coils and 7, respectively. Each of these sections is com posed of three sections of cables S. S) and l0 and l1, ,l2 and 13 respectively. Two ot these sections in each loadingy` .section` for example, 8 and 9 in section l and 1 1 and ll in section 5 are stranded according to the Dieseihorst-Martin system as shown in 14` l and the remaining section in each loadingT section (l0 and 13) is stranded according to the Star system.

lVhat is claimed is:

l. In a phantomed transmission system, a lumped loaded transmission line in which each loading section comprises a plurality of sections of quadded cable` one-third ol' the cable sections of each loaded section being quadded according to the Star system and the remainder accordingr to the Dicsellorst-hlartin system.

Q.. The method of controllingr the ratio of phantom to side circuit capacities in ay quadded cable line which comprises dividing the line into sections short with respect to the wave lengths of the wares to be transmitted and stranding portions of said sections in diiferent manners the lengths of said portions being so proportioned with respect to one another as to give the desired capacity ratio.

A method according to the next preceding claim in 'hich -said portions are stranded according to th(` Star and Dieselho'rst-hlartin systems.

In witness whereof, l hereunto subscribe my name this 27th day of May A. D., 1926.

MAX KI'R N. 

